Currently, this is also the simplest way:
Tensor<rank, dim> tens;
prm.add_parameter("Tensor", tens);
Take a look at the documentation of the add parameter method.
Patterns::Tools::to_string(tens);
And
Patterns::Tools::to_value
Are also available to simplify what you want to achieve.
Alternatively: Patterns::Tools::Convert offers ways to construct default
Patterns for many types, including Tensors.
Best,
Luca
> Il giorno 15 apr 2020, alle ore 14:57, Ahmad Shahba <ah.sha...@gmail.com> ha
> scritto:
>
>
> Ooops! The background was too dark :-)
>
> #include <deal.II/base/tensor.h>
> #include <deal.II/base/parameter_handler.h>
> #include <deal.II/base/utilities.h>
> #include <string>
> #include <iostream>
> #include <sstream>
>
> using namespace dealii;
>
> int main() {
>
>
> // Let's read this tensor from an istringstream. You may read it from
> istream in your
> // application
> std::istringstream is("set Tensor3x3 = 11, 12, 13, 21, 22, 23, 31, 32,
> 33");
>
>
> // Now let's set up the ParameterHandler object. Since you are reading
> 3x3 tensor, you are
> // dealing with 9 components and the default value should also have 9
> components (here 9
> // zeros) in it
> ParameterHandler prm;
>
> using Patterns::List;
> using Patterns::Double;
> prm.declare_entry("Tensor3x3",
> "0,0,0,0,0,0,0,0,0",
> List(Double(), 9, 9),
> "Tensor components");
>
>
> // Let's read it in now
> prm.parse_input(is);
> const std::string tensorString = prm.get("Tensor3x3");
>
> // Now let's split the string into individual components
> const std::vector<std::string> tensorComponentsString =
> Utilities::split_string_list(tensorString);
>
> // Now go over each component, convert it into double and put it in the
> tensor
> Tensor<2, 3> tensor;
> unsigned int counter = 0;
> for (unsigned ii = 0; ii < tensor.dimension; ++ii) {
> for (unsigned jj = 0; jj < tensor.dimension; ++jj) {
> tensor[ii][jj] =
> Utilities::string_to_double(tensorComponentsString[counter++]);
> }
> }
>
>
> // Let's check if we read the tensor correctly
> for (unsigned ii = 0; ii < tensor.dimension; ++ii) {
> for (unsigned jj = 0; jj < tensor.dimension; ++jj) {
> std::cout << "component [" << ii << ", " << jj << " ] = "
> << tensor[ii][jj] << std::endl;
> }
> }
>
>
> }
>
>
> Enter code here...
>
>
>
>> On Wednesday, April 15, 2020 at 8:53:55 AM UTC-4, Ahmad Shahba wrote:
>> Here is the code that does what I explained. I just switched up step 5 with
>> a much simpler approach. Note that you can simply make this into a
>> function/class template so that you could read general tensors, not just 3x3
>> tensors. I leave that to you :-)
>>
>> #include <deal.II/base/tensor.h>
>> #include <deal.II/base/parameter_handler.h>
>> #include <deal.II/base/utilities.h>
>> #include <string>
>> #include <iostream>
>> #include <sstream>
>>
>> using namespace dealii;
>>
>> int main() {
>>
>>
>> // Let's read this tensor from an istringstream. You may read it from
>> istream in your
>> // application
>> std::istringstream is("set Tensor3x3 = 11, 12, 13, 21, 22, 23, 31, 32,
>> 33");
>>
>>
>> // Now let's set up the ParameterHandler object. Since you are reading
>> 3x3 tensor, you are
>> // dealing with 9 components and the default value should also have 9
>> components (here 9
>> // zeros) in it
>> ParameterHandler prm;
>>
>> using Patterns::List;
>> using Patterns::Double;
>> prm.declare_entry("Tensor3x3",
>> "0,0,0,0,0,0,0,0,0",
>> List(Double(), 9, 9),
>> "Tensor components");
>>
>>
>> // Let's read it in now
>> prm.parse_input(is);
>> const std::string tensorString = prm.get("Tensor3x3");
>>
>> // Now let's split the string into individual components
>> const std::vector<std::string> tensorComponentsString =
>> Utilities::split_string_list(tensorString);
>>
>> // Now go over each component, convert it into double and put it in the
>> tensor
>> Tensor<2, 3> tensor;
>> unsigned int counter = 0;
>> for (unsigned ii = 0; ii < tensor.dimension; ++ii) {
>> for (unsigned jj = 0; jj < tensor.dimension; ++jj) {
>> tensor[ii][jj] =
>> Utilities::string_to_double(tensorComponentsString[counter++]);
>> }
>> }
>>
>>
>> // Let's check if we read the tensor correctly
>> for (unsigned ii = 0; ii < tensor.dimension; ++ii) {
>> for (unsigned jj = 0; jj < tensor.dimension; ++jj) {
>> std::cout << "component [" << ii << ", " << jj << " ] = "
>> << tensor[ii][jj] << std::endl;
>> }
>> }
>>
>>
>> }
>>
>>
>>
>>
>>
>>
>>> On Wednesday, April 15, 2020 at 3:54:57 AM UTC-4, Paras Kumar wrote:
>>> Ahmad,
>>>
>>>> On Tuesday, April 14, 2020 at 5:39:06 PM UTC+2, Ahmad Shahba wrote:
>>>> I don't know if it is the optimal way but I would use the following
>>>> approach
>>>> Read tensor components as Patterns::List
>>>> Use get method of ParameterHandler to read all tensor components as one
>>>> string into a string variable
>>>> Use split_string_list in the Utilities namespace to split the string
>>>> into individual components (still all components are strings)
>>>> Convert string-type components into doubles using string_to_double in
>>>> the Utilities namespace
>>>> Use Tensor (const Tensor< rank_, dim, OtherNumber > &initializer) to
>>>> construct the tensor
>>> Could you please elaborate on pointa 1 and 5, or share a code snippet which
>>> explains the process.
>>>
>>> Best,
>>> Paras
>
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